1. Field of the Invention
The present invention relates to a storage which is connected to a network and used, in particular to a NAS.
2. Description of the Related Art
As a method of improving performance of an information processing system, the number of computers provided in the information processing system is simply increased. However, if a large number of computers are used, considerable time and labor are required for supervision of the respective computers, and a total area for installing the computers and total power consumed by the computers increase considerably. In order to solve this problem, there has been devised a technique for setting a high performance computer, logically partitioning resources of the computer into plural sections, and using the respective partitioned sections as a virtual computer independently. This is called logical partitioning (LPAR) of a computer. For example, an example of such a logical partitioning technique is disclosed in JP-A-2003-157177 (corresponding U.S. Patent Publication No. 2003/0097393).
By virtualizing one computer look as if it is functioning as a large number of computers according to the logical partitioning, a flexible operation becomes possible. For example, various operating systems can be used on the respective virtual computers freely and boot up and shutdown or failure management can be performed independently for each virtual computer. In addition, the number of physical machines is small, which is advantageous in terms of system management, an installation area for the machines, power consumption thereof, and the like. However, in the LPAR in the conventional computer, although resources such as a processor and a memory in the computer are logically partitioned and allocated to the respective virtual computers, concerning a storage connected to the computer, a storage area provided in the storage is simply partitioned and the partitioned storage areas are allocated to the virtual computers, respectively. Nothing is further taken into account specifically.
On the other hand, as a form of using a storage, other than a form in which the storage is directly connected to one computer (hereinafter referred to as “host” in some cases) and used, there is a form in which the storage is shared by plural computers via a network. In the latter form, in particular, a storage which has an interface as a form of a file system, that is, to which file access is possible from the computers, is called a network attached storage (hereinafter referred to as “NAS).
Data is exchanged between the NAS and the hosts by a form of file having a name and a structure which are recognized by an operating system running on the host. Therefore, in addition to a disk drive for storing data and a control unit therefor, the NAS has a processor and a memory, which are used for translating file input/output to and from the host into data input/output to and from the disk drive.